1. Field of the Invention
The present invention relates to the field of inspection systems and in particular, to a system for inspection of containers.
2. Description of the Related Art
Travelers are familiar with carry-on luggage inspection systems. These systems typically allow a screener to X-ray carry-on luggage and other traveler items that the traveler places on a conveyor belt for inspection. Flexible curtains typically shield the entrance and exit of an X-ray scanning chamber. While in the chamber, a low-energy X-ray source irradiates the luggage, presenting an image on a display for the screener. The system typically requires the luggage to be stationary while being irradiated. Many airports use similar systems for checked luggage, in addition to carry-on items.
However, such systems are not typically suitable for screening large cargo containers or container transporters, such as large trucks. Low-energy X-rays may not be capable of penetrating the cargo containers or transporters. Further, conveyor belts used by luggage screening systems are typically not suitable for supporting the weight of fully loaded cargo containers or transporters. Previous techniques for screening of such cargo containers include personal inspection by an inspector and metal detection technology' as well as detection of contraband by high-energy X-ray systems.
The assignee of the present application has implemented a truck-transported cargo container inspection system for a customs agency in China. A radiation shield door at each end of a scanning tunnel blocks radiation from escaping the tunnel. At an entrance location, operators drive trucks onto intelligent platens mounted on rails, after which the driver exits the truck and walks to the exit around the tunnel. When the entrance door opens, the platen carrying the truck moves into the tunnel then stops and waits for the entrance door to close. The platen then starts moving again and passes by the scanner, which produces a display for the system operators. After scanning, the platen waits for the exit door to open, then exits, after which the exit doors close. The driver then returns to the truck, drives off the platen, and exits the area. The platen then returns to the loading area for a future truck. However, throughput of this system is limited because of the need to start and stop the platen to wait for the entrance door and the exit door to open and close, with only one platen allowed in the tunnel at a time. In addition, the platens, which are self-propelled intelligent platens coupled to complex power delivery systems by trailing electrical leads or moving electrical pickup systems, can present reliability concerns.